The present invention relates to floating bodies and in particular to spherical floating bodies employed as oceanic and deep water loading terminals, drill rigs and movable as well as stationary bulk cargo vessels.
It has recently been advanced in U.S. Pat. No. 3,487,484 granted Jan. 6, 1970 to J. F. Holmes, entitled "Tuned Floating Bodies" that if a sphere be made of suitable size, with its weight distributed in such a way that its natural period of oscillation about a horizontal diameter is much longer than the period of any waves that it is likely to encounter, that the body would in fact follow the vertical and translateral movement of the waves but exhibit little or no roll. It has been suggested to use such spheres as floating bodies to house floating power plants, offshore drill rigs, light houses and similar vessels which are intended to be substantially stationary in position or at best moveable at slow speeds over limited distances.
One problem not overcome by the aforementioned patent is the effect of ocean wave "Heave" on the sphere. That is the rhythmic movement of the sphere in a vertical up and down motion caused by the actual rising and falling of the succeeding waves. In offshore drilling rigs this vertical motion must be maintained within relatively narrow limits if successful and economic drilling operations are to be performed. It has been normal practice to compensate for "Heave" in this instance by increasing the weight of the vessel, hence, the structure necessary to support this weight. This cascading of events is avoided by the instant invention. In other applications of the sphere, for instance in housing of floating reactor power plants, heave accelerations must be limited to avoid acceleration loading and consequent subsequent wear of bearings in rotating machinery.
In a paper entitle "Drillship Designed for Heavy Seas" in the February 1972 Ocean Industry, target Roll and Heave standards were set which establish that for 80% of the necessary drill operations a roll of as much as 14.degree. and a 5 to 7 foot double amplitude heave can be sustained. For certain other operations the maximum roll and heave cannot exceed 2.2.degree. and 2.7 feet.
It is the general object of the present invention to provide a spherical body tuned to avoid roll which is simultaneously provided with means by which heave is eliminated under virtually all sea states and deep water conditions.
It is an object of this invention to provide a tuned sphere, having an integral structural configuration which effectively and fully limits heave.
It is another object of the invention to provide a floating sphere, tuned simultaneously against roll and heave, thus providing a stable, floating vessel capable of being employed as support for drill rigs, power plants, or other oceanic structures, as well as bulk cargo vessels.
It is a specific object of the present invention to provide a tuned sphere with means for fully limiting heave to predetermined values which means is adjustable so as to be controllable with respect to specific sea conditions.
It is of course, an object of this invention to provide a tuned sphere having means for eliminating heave which is simple and relatively light in weight.
Other objects and advantages of the present invention will be seen from the following disclosure.